Lactose or milk sugar is obtained by crystallization from a milk derived source such as cheese whey. Whey as a byproduct of cheese manufacture is available in about 3.5 billion gallons per year. Numerous methods have been devised to extract the valuable lactose and protein from whey. In one method, whey protein is concentrated by passing the whey through an ultrafiltration membrane. The protein is removed leaving the lactose rich permeate. Lactose crystallized in the conventional manner from whey contains impurities. Protein, salts, riboflavin (a coloring matter), present during the conventional crystallization process contaminate the lactose, especially, if they become insoluble during the process of concentrating the permeate.
A relationship between riboflavin absorption by lactose and the lactose concentration of whey has been disclosed by Leviton in Volume 36, Industrial and Engineering Chemistry, pg. 744. In discussing the added influence of temperature on the absorption of riboflavin by lactose, Leviton discloses that it is possible to crystallize a portion of lactose free of riboflavin. A process incorporating the teachings of Leviton, however, would be commercially unacceptable due to the low lactose yields which result.
USP lactose is conventionally produced from edible grade lactose by dissolving the edible grade lactose in hot water, treating the solution with activated charcoals and filtering the solution using a diatomaceous earth filter to remove the impurities. The lactose is then recrystallized from the supersaturated solution, centrifuged, washed and dried to produce the white appearing USP lactose. The conventional process described above is time consuming and not cost effective.
It is therefore, an object of the present invention to devise a less complex and more cost effective method of producing USP quality lactose.